Method and apparatus for protecting the electrodes in arc-furnaces.



J. I. BRONN z W. SOHEMMANN. METHOD AND APPARATUS FOR PROTEGTING THE ELEGTRODBS IN ARC PURNAGBS.

APPLICATION FILED DEO.16, 1913.

Patente Feb. 23, 1915.

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METHOB AND APPARTUS FOR PROTECTING- THE ELECTRODES IN ARC-FURNACES;

specification of Letters Patent.

Patented Feb., 23, 19156 Application filed December 16, 1913. Serial No. 807,103.

T0 aZZ wlzom t may oonccrn Be it known that we, JnGoR TSRAEL BRONN and WILHELM SCHEMMANN, both citizens of the German Empire, and residents of Rombach, Lorraine, Germany, with the post-office addresses Gartenstrasse' 17 and Httenstrasse 7 respectively, have invented new and useful Improvementsin Methods and Apparatus for Protecting the Electrodes in Arc-Furnaces, of which the following is a specification.

In electric fuE-naces into which the electrodes project through the arch or walls, the

internal dimensions of the apertures through which said electrodes pass must be somewhat greater than those of the sectional area of the electrodes, so that an annular space is left between the electrode and the wall. K The inevitable result is that the gl'owing' furnace gases and flames issue'through these spaces and heat the exterior portions of the electrodes to such an extent as to cause combustion of the upper portion of the carbon electrodes in the outer air; In this way the sectional area of the electrodes is dir'ninished at the alfected parts, and this reduction of section leads to the further overheating of these reduced portions, in accordance with Joulds law of the heat generated by currents. The electrodes are therefore overheated and consumed both within and without at the same time; and their sectional area may be reduced to such an extent that the carbon,

breaks off. In order to remedy this drawback it is the general practice tol use a hollow metal ring through which water 1s passed, as shownnt a in the case of electrode in the accompanying drawing which shows a sectional lelevation of a furnace.

Since the internal diameter of'this cooling ring must beikept somewhat greater' than the diameter of the electrode, in order to insure reliable working and also because of the inequa'lity existing between individual electrodes, afree space of about 10 to 15 millimeters in width is unavoidable between the electrode T of the drawing), even when the i cooling'rings are used,c Now, when an electrode is advanced farther into the ;furnace to compensate for the consumption of its lower extremity, the cooling ring surrounds that part of thelelectrode which is reduced in diameter and the free space becomes much wider and the fiames from the furnace may endanger, or at least injure, not only the carbon electrode but also the current leads 0.' Moreover, the use of packings and devices of the stufling-box type have failed to act in the long run. On the other hand the measures described below and illustrated in connection with the electrodes H and TH on the accompanying drawing, have been found very efiective. In order to prevent the furnace fiame from issuing through the free space between the cooling ring and the electrode, aihol'low circular body, for examplev an annular tube d, is. arranged above the cooling ring a, which hollow body need not surround the electrode very closely. This hollow body d is provided on its inner wall with numerous openings or nozzles e, from which an incombustible gas of any kind, such for instance as nitrogen, ;carbon dioXid, smoke or fiue gases and water vapor are directed, under pressure, against the electrode. The vresulting excess pressure over that within the furnace (which excess may be very small) created around the electrode preventsI the escape of the furnace fiames and thus completely obviates the drawbacks in question.

Remarkably enough, it has been found that atmospheric air can be used in place of the inert and incombustible gases mentioned above, without any injury to the carbon of the electrodes, and the fear that a current of air '-directed against the carbon electrodes (which are very hot in consequence of the heat of the furnace and of the passage of the current therethrough) might oxidize, or even burn, the electrodes at this point, has been found to be ill-founded. The absence of the dreaded injurious action of the air is probably due to the intense cooling ofthe compressed air, as the result ofv its Sudden expansion on issuing from the nozzles. On the other hand, the favorable efiect may also be facilitated, by the fact that the furnace flame is cooled down quickly by the relatively large volume of cold gas, or is to some extent extinguished when water vapor is used.

In many cases the cooling ring a, hitherto I generally used, may be dispensed with entirely and, in place of this, as is thecase with electrode III, oneofthe specified gases,

or mixtures of same is caused to, lmpinge against the electrode from the hollow body f/ provided with nozzles or slits.

Instead of providing an'excess pressure around each electrode, such excess pressure may be provided about the entire arch of the furnace, and therefore also about all the' free spaces surrounding the electrodes, by allowing compressed air, etc., to issue from nozzles situated in the vicini-ty of the fur`- tendency to oxidize and therefore need to be protected therefrom, `it is advisable, When using air, carbon dioxid, water, or water vapor, as described above, to cover the bath of molten metal with a layer, of coke breeze o or the like to make sure of-preventing oxidation by keeping 'the oxygeniferous gases' from acting on the bath. If no steam boiler is available in the v1- cinity of the electric furnace, or when the available steam is too wet, the considerable quantities of heat which are radiated o from the walls of the electric furnace and would otherwise be wasted, can/ be utilized for the production of dry steam. This may be done, for example, by p'rovlding in the 'furnace walls, tubes W in'which the water may be raised 'to boiling temperatures, or

` tubes V for superheating .the steam. In several forms of furnace the iron Shell of the vfurnace 'may be wholly ,or partiall'y arran'ged as a jacket.

Now what we claim and desire to secure by Letters Patent is the following:

i. The method of protecting exposed loosefitting electrodes 'of 'electric arc furnaces from the action of furnace gases tending to escape through theL openings surrounding the electrodes, which conslsts in generating.

and maintaining a flow of fluid about the electrodes adjacent said openings, under' generated in the 'pressure in excess of that furnace.

- 2: The methodof protecting exposed loosefitting electrodes of' electric arc furnaces from the action of furnace gases tending to :escape through the openings surrounding the electrodes, which consists in generating and maintaining a flow of gas about the.

electrodes adjacent said openings, under pressure in'excess of that generated. in the furnace.

3. The method of protecting exposed loosefitting electrodes of electric arc furnaces from the action of furnace gases tending to escape through the openings surrounding the electrodes, which vconsists in generating and maintaining a flow of incombustible gas about the electrodes 'adj acent said openings, lunder pressure in exces's of that generated in electric furnaces consisting in causingy steam to impinge against the electrodes at the points Where the electrodeskenter the furnace and using the heat radiating from the furnace to generate the steam.

6. The method of protecting the electrodes in electric furnaces consisting in causing steam to impinge against the electrodes at the points Where the electrodes enter `the furnace and using the heat radiating from the furnace to overheat the steam.

7. Means for protecting the electrodes in electric-arc furnaces, said means consisting of a hollow body adapted to' surround the electrodes abovethe pointswhere said electrodes enter the furnace, said hollow body being formed with apertures at the inner side thereof and means for supplying gaseous medium to said hollow body.

In testimony, that we claim the foregoing as our' invention, we have signed our names in presence of two witnesses, this 2nd day of December, 1913.

JEGoR i'sRAEL BRoNN. WILHELM soHEMMANN.

Witnesses I ALBERT TEICHMLLER, Louis w VANDORY. 

